– Decreased secretion of parathyroid hormone by the parathyroid glands, manifested as hypocalcemia.
Causes and Incidence
The cause is usually unintentional damage to or removal of the parathyroid glands during thyroidectomy. There is a rare idiopathic form in which the parathyroids are absent or atrophied, as well as a genetic form that is part of a polyendocrine syndrome called HAM (hypoparathyroidism, Addison’s disease, and moniliasis). The idiopathic form generally occurs in childhood.
A decrease in the secretion of parathyroid hormone (PTH) leads to a reduced resorption of calcium from the renal tubules, decreased absorption of calcium in the gastrointestinal (GI) tract, and decreased resorption of calcium from bone. The serum calcium level falls, increasing neuromuscular excitability and leading to spasms and tetany.
Hypoparathyroidism is often asymptomatic in the early stages. The most characteristic sign is tetany with paresthesias of the lips, tongue, fingers, and feet; other signs are carpopedal and facial spasms, generalized muscle aches, and fatigue. Encephalopathy, depression, dementia, and papilledema may also be present.
Acute onset of hypocalcemia leads to laryngospasm, airway obstruction, and cardiac failure. Long-standing disease leads to bone deformities, cataract formation, reduced cardiac contractility, and heart failure. Childhood disease can lead to mental retardation and stunted growth.
Parathyroid deficiency is characterized by a low serum calcium level, high serum phosphorus level, and normal alkaline phosphatase level. Serum intact PTH is decreased. Chvostek’s and Trousseau’s signs are positive.
Calcium supplements; vitamin D to increase calcium absorption in the GI tract.
Calcium-rich diet; monitoring of calcium levels.